linux-kernel - Re: [patch] mm: memcg: update the correct soft limit tree during migration

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Message-ID: <20120116124308.GA25981@shutemov.name>
Date:	Mon, 16 Jan 2012 14:43:08 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] mm: memcg: update the correct soft limit tree during
 migration

On Fri, Jan 13, 2012 at 04:41:31PM +0100, Johannes Weiner wrote:
> end_migration() passes the old page instead of the new page to commit
> the charge.  This page descriptor is not used for committing itself,
> though, since we also pass the (correct) page_cgroup descriptor.  But
> it's used to find the soft limit tree through the page's zone, so the
> soft limit tree of the old page's zone is updated instead of that of
> the new page's, which might get slightly out of date until the next
> charge reaches the ratelimit point.
> 
> This glitch has been present since '5564e88 memcg: condense
> page_cgroup-to-page lookup points'.
> 
> Reported-by: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Kirill A. Shutemov <kirill@...temov.name>


-- 
 Kirill A. Shutemov
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